Manufacturing panels for floor or wall coverings is a very delicate process wherein, next to materials choice and quality of the raw materials, optimum operating parameters determine the good quality of the laminate panels. Such panels are desirable for wall and floor coverings in both domestic and industrial environment. Important properties of said panels are, inter alia, dimensional stability, flexural stiffness, resistance to curling and water resistance. Depending on the specific application of the panels, however, the properties need to be optimized. This optimization can be done by selecting the appropriate extrusion parameters, as well as by the reduction of material and energy losses. The suitable set-up of screws and dies is of fundamental importance.
For example, U.S. Pat. No. 7,318,720 discloses an improved die assembly for the extrusion of thermoplastic resin comprising cellulose-fibre composite profiles, wherein the die assembly is selected in such a way so as to minimize the risk of melt fracture at the surface of the extruded composite profile. The die assembly according to the invention comprises a balanced flow passage having a heated compression zone, a heated transition zone, a heated converging die zone and a die which corresponds to at least a portion of the downstream end of the flow passage and which is cooled to the temperature below the melting point of the thermoplastic resin.
The invention also discloses a production process for composite profiles comprising the steps of providing resin and fibre, thereby providing a composite compound, processing the compound through an extrusion system, extruding the compound through the die assembly to form the desired profile, cooling the profile, and cutting it to length.
Such optimized die assemblies are very specific depending on the implementation. For the use of extruders for producing panels for floor or wall panels, parameters such as mixing capacity and flow rate are of the highest importance. This means that a highly homogenized extruded mass must be ensured without an all too high risk of process interruptions as a result of, for example, melt fracture, and which can preferably be produced at sufficiently high flow rates. The reduction of unnecessary energy and material losses should also be taken into account. However, the prior art does not or does not adequately provide a solution to one or more of the afore-mentioned problems.